The invention relates to a apparatus for treating substrates, in which the latter are immersed for some time in bath containing a liquid and are then taken therefrom so lowly that practically the whole quantity of liquid remains in the bath.
Apparatus of this kind may be used in the manufacture of electric circuits on all kinds of substrates, such as, for example, integrated circuits on semiconductor wafers (for example of silicon), drives for liquid crystal displays on transparent plates of glass or quartz or circuits on plates of synthetic material (circuit boards). The method may also be used in the manufacture of shadow masks for television picture tubes or in the manufacture of CD or VLP records. In all these cases, the substrates are immersed many times for some time in a bath containing a liquid, for example in galvanic baths for deposition of metals, in etching baths for etching patterns into metal layers or into semiconductor material, in development baths for developing exposed photolacquer layers and in rinsing baths for cleaning the substrates. After treatment in the liquid baths, the substrates are taken from the liquid and are dried. The substrates can be taken from the liquid by lifting or withdrawing from the liquid, and by causing the liquid to flow out of the bath.
U.S. Pat. No. 4,722,752 discloses a method in which silicon wafers are immersed for some time for cleaning in a liquid containing hot (90.degree. C.) deionized water. Subsequently, the silicon wafers are lifted from the water slowly (at a speed of about 5 cm/min. This speed is sufficiently low to ensure that the silicon wafers leave the bath in practically dry state. The surface tension then should play a part.
It has been found in practice that in this method of drying contaminations from the liquid can remain on the substrates. It has been found that with the known method described a water film having a thickness a few microns remains on the silicon wafers. This water film then evaporates rapidly, but this may give rise to so-called "drying marks". During drying, the water film can be contracted so that contaminations in the water, which are often of organic or metallic nature, remain in local concentration on the wafers. Such residues can be very disturbing if, for example, the wafers must still be subjected to an etching treatment. They can locally delay the etching treatment or even prevent this treatment. Further, dust particles present in the water film also remain on the wafers.